Heat spreader and heat dissipation device using same

ABSTRACT

A heat dissipation fan includes a fan frame, a bearing assembly, a stator and a rotor. The fan frame includes a base and a central tube. The central tube includes an open top end and an open bottom end. The base defines a receiving concave at a bottom surface thereof. The receiving concave communicates with the central hole. A top wall is formed by the base over the concave. A sidewall is formed between the top wall and the bottom surface of the base and surrounds the concave. A plurality of first locking units extend from the top wall into the receiving concave. The bearing assembly includes an oil sealing cover for sealing the open bottom end of the central tube. The oil sealing cover includes a plurality of second locking units which are detachably interlocked with the first locking units to mount the oil sealing cover to the base.

BACKGROUND

1. Technical Field

The present disclosure relates to heat spreaders, and more particularly to a heat spreader for transferring heat of a heat generating electronic component and a heat dissipation device using same.

2. Description of Related Art

Nowadays, heat sinks are used in electronic products for dissipating heat generated by electronic components such as CPUs. Typically, a heat spreader made of metals having a high thermal conductivity is configured for distributing and transferring heat from the CPU to the heat sink. The heat spreader is arranged to have an intimate contact with the electronic component and absorbs heat therefrom.

However, the electronic components are made to be more powerful while occupying a smaller size. Thus, a contacting area between the electronic component and the heat spreader is decreased as the size of the electronic component decreases. Therefore, a heat flux density between a contacting portion of the heat spreader and other portions of the heat spreader is increased. As the CPU operates faster and faster, and, therefore generates larger and larger amount of heat, the conventional heat spreader, which transfers heat via heat conduction means, cannot transfer heat to the heat sink uniformly to meet the increased heat dissipating requirement of the CPU.

For the foregoing reasons, therefore, there is a need in the art for a heat spreader which overcomes the above-mentioned problems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembled, isometric view of a heat dissipation device in accordance with a first embodiment.

FIG. 2 is an exploded view of the heat dissipation device of FIG. 1.

FIG. 3 is a cross-section of the heat dissipation device of FIG. 1, taken along line III-III thereof.

FIG. 4 is an exploded view of a heat spreader of a heat dissipation device in accordance with a second embodiment.

FIG. 5 is a cross-section of a heat dissipation device in accordance with a third embodiment.

DETAILED DESCRIPTION

Reference will now be made to the drawing figures to describe the present heat dissipation device in detail.

Referring to FIGS. 1 and 2, a heat dissipation device 10 in accordance with a first embodiment of the disclosure is shown. The heat dissipation device 10 is mounted on a heat generating electronic component 40 such as a CPU (central processing unit), a North Bridge chip or an LED (light emitting diode) to dissipate heat therefrom. The heat dissipation device 10 includes a heat spreader 20 and a heat sink 30 mounted on the heat spreader 20.

The heat spreader 20 has a flat type configuration and is rectangular shaped when viewed from above. The heat spreader 20 includes a main plate 21 and a first and a second end covers 23 located at front and rear sides of the main plate 21, respectively. The main plate 21 has a flat rectangular bottom surface 212 (FIG. 3) contacting the electronic component 40 and an opposite top surface 211. The main plate 21 defines a plurality of through holes 25 in an interior thereof. The through holes 25 are parallel to and spaced from each other. The through holes 25 are arranged side by side along a left-to-right direction of the main plate 21. Each of the through holes 25 has a circular cross section and includes an evaporator section at a middle portion of the main plate 21 and two condenser sections adjacent to the front and rear sides of the main plate 21, respectively. A first and a second receiving grooves 24 are defined at the front and rear sides of the main plate 21, respectively. The receiving grooves 24 are concaved inwardly from the front and rear sides of the main plate 21. Each of the through holes 25 extends horizontally along a front-to-rear direction of the main plate 21 to communicate the first receiving groove 24 with the second receiving groove 24. An annular wick structure 26 (FIG. 3) is disposed in each of the through holes 25 and contacts an inner surface of the main plate 21. The wick structures 26 are selected from a porous structure such as grooves, sintered powder, screen mesh, or bundles of fiber to provide capillary force in the through holes 25. The through holes 25 can be provided with different kinds of wick structure therein, according to the actual heat dissipation requirement. Each of the receiving grooves 24 is rectangular and elongated. A diameter of each of the through holes 25 is smaller than a height of the receiving grooves 24. A width of an occupying region of the through holes 25 along the left-to-right direction of the main plate 21 is smaller than a length of the receiving groove 24.

Each of the end covers 23 includes a rectangular sealed portion 231 and a plurality of connecting portions 233 extending horizontally from an inner side surface of the sealed portion 231 towards the main plate 21. The sealed portion 231 of each end cover 23 has a size substantially equal to a size of each of the first and the second receiving grooves 24 of the main plate 21. Each of the connecting portions 233 is column. The connecting portions 233 of each of the end covers 23 are paralleled to and spaced from each other. The connecting portions 233 are arranged along a left-to-right direction of the inner side surface of the sealed portion 231 and face the through holes 25 correspondingly. Number of the connecting portions 233 of each of the end covers 23 equals to the number of the through holes 25 of the main plate 21. A diameter of each of the connecting portions 233 is slightly larger than the diameter of each of the through holes 25. The connecting portions 233 of the end covers 23 can be inserted into distal ends of the through holes 25, respectively. Thus, the end covers 23 connect with the main plate 21 by interference fit of the connecting portions 233 in the through holes 25. Accordingly, the distal ends of each through hole 25 are sealed by the connecting portions 233 of the end covers 23, respectively.

Alternatively, the diameter of each of the connecting portions 233 can be slightly smaller than the diameter of each of the through holes 25. Solders can be sprayed on an outer surface of connecting portions 233 or the inner surface of the main plate 21 at the distal ends of the through holes 25, thus the end covers 23 and the main plate 21 can be connected with each other by soldering. A plurality of hermetical channels are thus formed in the interior of the main plate 21 by the through holes 25. The wick structures 26 are layered on the inner surfaces of the hermetically channels. Subsequently, the hermetically channels are evacuated and then injected with working medium 29 therein which has a lower boiling point and is compatible with the wick structures 26. The working medium 29 can be selected from a liquid such as water, alcohol, or methanol.

The heat sink 30 includes a plurality of parallel fins 31 arranged side by side on the top surface 211 of the base plate 21. Each of the fins 31 extends along the same direction as the through holes 25. That is, each of the fins 31 extends along the front-to-rear direction of the main plate 21. Referring to FIG. 3, each of the fins 31 includes a plate-shaped main body 311 and a flange 312 extending perpendicularly from a bottom end of the main body 311 to a neighboring fin 31. The flanges 312 cooperatively form a planar bottom surface at a bottom side of the heat sink 30 for increasing a contacting area between the top surface 211 of the main plate 21 and the heat sink 30.

In operation of the heat dissipation device 10, the electronic component 40 is disposed under and has an intimate contact with a central portion of the bottom surface 212 of the main plate 21. A substantially rectangular shaped heating area 27 is formed at the central portion of the bottom surface 212 of the heat spreader 20, absorbing heat from the electronic component 40. A spreading area 28 surrounding the heating area 27 is thus formed at an outer periphery of the heat spreader 20 for transferring the heat to the heat sink 30 and dissipating the heat to surrounding environment.

The working medium 29 contained in the evaporator sections of the through holes 25 corresponding to the heating area 27 vaporizes due to the heat absorbed from the electronic component 40. The vapor then spreads to fill the hermetically channels of the main plate 21, and wherever the vapor comes into contact with the condenser sections of the through holes 25 corresponding to the spreading area 28 of the main plate 21, it releases its latent heat of vaporization and condenses. Simultaneously, the vapor moves upwardly to transfer the heat to the fins 31 above the heating area 27. The heat is therefore spread on the entire heat spreader 20 quickly and uniformly, and thus can be evenly transferred to each fin 31 of the heat sink 30 for dissipating to surrounding environment. The condensate returns to the heating area 27 due to the capillary forces generated by the wick structures 26. Thereafter, the condensate continues to vaporize and condense, thereby removing the heat generated by the electronic component 40.

In the present heat spreader 20, the main plate 21 defines the plurality of through holes 25 containing working fluid and wick structure 26 therein, the heat generated by the heat generating electronic component 40 can be quickly absorbed by the working medium 29 contained in through holes 25, since the lowest heat resistance between the electronic component 40 and the main plate 21 and the large contacting areas between wick structures 26 and the main plate 21. The through holes 25 and the wick structures 26 thereof help the working medium 29 contained in the main plate 21 to horizontally move in the main plate 21 from the heating area 27 of the heat spreader 20 to the spreading area 28 due to their low heat resistance. The through holes 25 and the wick structures 26 thereof also help the heat transfer to the fins 31 on the top surface 211 of the heat spreader 20 with low heat resistance, and therefore mounts of heat generated by the electronic component 40 is quickly and effectively transferred to different portions of the heat sink 30 far from the electronic component 40. This increases the heat transfer capability of the heat spreader 20 greatly, and thereby increasing the heat dissipation efficiency of the heat dissipation device 10.

FIG. 4 is an exploded view of a heat spreader 20 a in accordance with a second embodiment of the disclosure, differing from the previous heat spreader 20 only in that a main plate 21 a defines one receiving groove 24 at a front side and forms a close surface at a rear side, through holes 25 a defined in an interior of the main plate 21 a each have an open end communicated with the receiving groove 24 and a close end corresponding to the close rear surface, and accordingly only one end cover 23 is in included at the front side of the main plate 21 a for sealing the open ends of the through holes 25 a.

FIG. 5 is a cross-section of a heat dissipation device 10 b in accordance with a third embodiment of the disclosure, differing from the previous heat dissipation device 10 only in that the fins 31 b and the main plate 21 b of the heat spreader 20 b are integrally formed by extrusion, and each of the fins 31 b includes a plate-shaped main body 311 b extending upwardly and perpendicularly from a top surface 211 b of the main plate 21 b. In the present heat dissipation device 10 b, lower heat resistance between the main plate 21 b and the fins 31 b can be obtained, and thus heat transfer to the fins 31 b on the top surface 211 b of the main plate 21 b can be very quick for further increasing the heat dissipation efficiency of the heat dissipation device 10 b.

It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A heat dissipation device comprising: a heat spreader comprising a main plate and an end cover coupling to one lateral side of the main plate, the main plate defining a plurality of parallel through holes therein, each of the through holes having an open end facing the lateral side of the main plate, a plurality of wick structures being respectively disposed in the through holes, the end cover sealing the open ends of the through holes to form a plurality of hermetical channels in the spreader, a working medium being contained in each of the channels; and a plurality of fins arranged on a surface of the main plate perpendicular to the lateral side.
 2. The heat dissipation device of claim 1, wherein each of the through holes has a second open end facing another lateral side of the main plate opposite to the lateral side, the heat spreader further comprising a second end cover located at the another lateral side of the main plate for sealing the second open ends of the through holes, each of the end covers comprising a plurality of connecting portions received in the open ends of the through holes, respectively.
 3. The heat dissipation device of claim 2, wherein each of the connecting portions has a diameter lager than a diameter of each of the through holes, the end covers connected with the main plate by interference fit between the connecting portions and the open ends of the through holes.
 4. The heat dissipation device of claim 2, wherein each of the connecting portions has a diameter smaller than a diameter of each of the through holes, the end covers connected with the main plate by soldering filled between each connecting portion and an inner surface of the main plate at the open ends of a corresponding through hole.
 5. The heat dissipation device of claim 2, wherein the main plate defines a first and a second receiving grooves at the two lateral sides thereof, respectively, each of the through holes communicating the first receiving groove with the second receiving groove, each of the end covers comprising a sealed portion received in a corresponding one of the first and the second receiving grooves, the connecting portions extending from the sealed portions into the through holes.
 6. The heat dissipation device of claim 5, wherein each of the receiving grooves is rectangular, the through holes are arranged in the main plate side by side, a height of the receiving groove is larger than a diameter of each of the through holes, and a length of the receiving groove is larger than a width of an occupying area of the through holes.
 7. The heat dissipation device of claim 1, wherein each of the fins comprises a plate-shaped main body extending upwardly from the top surface of the main plate, the main body being parallel to the through holes.
 8. The heat dissipation device of claim 1, wherein each of the fins comprises a main body and a flange extending perpendicularly from a bottom end of the main body to a neighboring fin, the flanges cooperatively forming a planar surface contacting the top surface of the main plate.
 9. A heat spreader comprising: a main plate defining a plurality of parallel through holes in an interior thereof, each of the through holes communicated with two opposite lateral sides of the main plate; two end covers located at the two lateral sides of the main plate, each of the end covers comprising a plurality of connecting portions received in distal ends of the through holes for sealing the through holes; a plurality of wick structures disposed in the through holes and contacting an inner surface of the main plate; and a working medium being contained in each of the through holes.
 10. The heat spreader of claim 9, wherein the main plate defines two receiving grooves at the two lateral sides of the main plate, respectively, distal ends of each through hole communicated with the two receiving grooves respectively, each of the end covers comprising a sealed portion received in a corresponding receiving groove.
 11. The heat spreader of claim 10, wherein the connecting portions extend from one surface of the sealed portion facing the main plate towards the distal ends of the through holes, respectively.
 12. The heat spreader of claim 10, wherein each of the receiving grooves is rectangular, each of the sealed portions has a shape and a size corresponding to those of the each of the receiving grooves. 